presentation valves

8/8/2019 Presentation Valves

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VALVEVALVE

A valve is a mechanical device that controls the A valve is a mechanical device that controls theflow of fluid and pressure within a system or flow of fluid and pressure within a system or process. A valve controls system or processprocess. A valve controls system or processfluid flow and pressure by performing any of thefluid flow and pressure by performing any of thefollowing functions:following functions:

1.1. Stopping and starting fluid flowStopping and starting fluid flow2.2. Varying (throttling) the amount of fluid flowVarying (throttling) the amount of fluid flow3.3. Controlling the direction of fluid flowControlling the direction of fluid flow


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P ARTS OF VALVEP ARTS OF VALVE

1. Body2. Bonnet

3. Stem4. Actuator 5. Packing6. Seat7. Disk


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VALVE BODYVALVE BODY

The body, sometimes called the shell, itThe body, sometimes called the shell, it

is the principal element of a valveis the principal element of a valveassemblybecause it is the frameworkthatassemblybecause it is the frameworkthatholds everything it resists fluid pressureholds everything it resists fluid pressureloads from connecting piping. It receivesloads from connecting piping. It receivesinlet and outlet piping through threaded,inlet and outlet piping through threaded,bolted, or welded joints.bolted, or welded joints.


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Valve bodies are cast or forged into aValve bodies are cast or forged into avariety of shapes. Although a spherevariety of shapes. Although a sphere

or a cylinder would theoretically beor a cylinder would theoretically bethe most economical shape to resistthe most economical shape to resistfluid pressure when a valve is openfluid pressure when a valve is open


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BonnetBonnet

A A b onnetb onnet acts as a cover on the valve body.acts as a cover on the valve body.It is commonly semiIt is commonly semi- -permanently screwedpermanently screwed

into the valve body. During manufacture of into the valve body. During manufacture of the valve, the internal parts are put into thethe valve, the internal parts are put into thebody and then the bonnet is attached tobody and then the bonnet is attached tohold everything together inside.hold everything together inside.


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STEMSTEMTheThe stemstem , which connects the actuator and, which connects the actuator and

disk, is responsible for positioning the disk.disk, is responsible for positioning the disk.Stems are typically forged and connected toStems are typically forged and connected to

the disk by threaded or welded joints.the disk by threaded or welded joints.


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TYP ES OF STEMSTYP ES OF STEMS

Two types of valve stems are rising stemsTwo types of valve stems are rising stemsand nonrising stems. these two types of and nonrising stems. these two types of stems are easily distinguished bystems are easily distinguished byobservation. For a rising stem valve, theobservation. For a rising stem valve, thestem will rise above the actuator as thestem will rise above the actuator as thevalve is opened. There is no upward stemvalve is opened. There is no upward stemmovement from outside the valve for amovement from outside the valve for anonrising stem design.nonrising stem design.


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VALVE TRIMVALVE TRIM

The internal elements of a valve areThe internal elements of a valve arecollectively referred to as a valve'scollectively referred to as a valve's trimtrimThe trim typically includes a disk, seat andThe trim typically includes a disk, seat andstem. A valve's performance is determinedstem. A valve's performance is determinedby the disk and seat interface and theby the disk and seat interface and therelation of the disk position to the seat.relation of the disk position to the seat.


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ACTUATOR ACTUATOR

The actuator operates the stem and diskThe actuator operates the stem and diskassembly. An actuator may be a manuallyassembly. An actuator may be a manuallyoperated handwheel, manual lever, motor operated handwheel, manual lever, motor operator, solenoid operator, pneumaticoperator, solenoid operator, pneumaticoperator, or hydraulicram. In someoperator, or hydraulicram. In somedesigns, the actuator is supported by thedesigns, the actuator is supported by thebonnet. In other designs, a yoke mountedbonnet. In other designs, a yoke mountedto the bonnet supports the actuator.to the bonnet supports the actuator.


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P ACKINGP ACKING

Most valves use some form of packing toMost valves use some form of packing toprevent leakage from the space betweenprevent leakage from the space betweenthe stem and the bonnet.the stem and the bonnet. Pack ing Pack ing isiscommonly a fibrous material (such as flax)commonly a fibrous material (such as flax)or another compound (such as teflon) thator another compound (such as teflon) thatforms a seal between the internal parts of forms a seal between the internal parts of a valve and the outside where the stema valve and the outside where the stem


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Valve packing must be properly compressedValve packing must be properly compressedto prevent fluid loss and damage to theto prevent fluid loss and damage to thevalve's stem. If a valve's packing is toovalve's stem. If a valve's packing is tooloose, the valve will leak, which is a safetyloose, the valve will leak, which is a safetyhazard. If the packing is too tight, it willhazard. If the packing is too tight, it willimpair the movement and possiblyimpair the movement and possiblydamage the stem.damage the stem.


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TYP ES OF VALVESTYP ES OF VALVES

GATE VALVEGATE VALVEBALL VALVEBALL VALVE

P LUG VALVEP LUG VALVEBUTTERFLY VALVEBUTTERFLY VALVENEEDLE VALVENEEDLE VALVE

DIAPH RAM VALVEDIAPH RAM VALVE


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GATE VALVEGATE VALVE

A g a te valve is a linear motion valve used to startor stop fluid flow; however, it does not

regulate or throttle flow. The name gate is derivedfrom the appearance of the disk in the flow

stream..The disk of a gate valve is completely removed

from the flow stream when the valve is fullyopen.


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This characteristic offers virtually no resistance to flowwhen the valve is open. H ence,

there is little pressure drop across an open gate valve.When the valve is fully closed, a disk-to-seal ring contact

surface exists for 360, and goodsealing is provided. With the proper of a disk to the seal

ring, very little or no leakageoccurs across the disk when the gate valve is closed.


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When the valve is fully closed,. With theproper mating of a disk to the seal ring,very little or no leakage

occurs across the disk when the gate valveis closed.


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BALL VALVEBALL VALVE

A ball valve is a rotational motion valve thatuses a ball-shaped disk to stop or start fluidflow.

The ball performs the same function as the diskin the globe valve. When the valve handle isturned to open the valve, the ball rotates to apoint where the hole through the ball is in linewith the valve body inlet and outlet. When thevalve is shut, the ball is rotated\so that the holeis perpendicular to the flow openings of thevalve body and the flow is stopped


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P LUG VALVEP LUG VALVE

A plug valve is a rotational motion valve used tostop or start fluid flow. The name is derived

from the shape of the disk, which resembles aplug. A plug valve is shown in Figure. The

simplest form of a plug valve is the petcock. Thebody of a plug valve is machined to receive

the tapered or cylindrical plug.


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The disk is a solid plug with a bored passage at aright angle to

the longitudinal axis of the plug.In the open position, the passage in the plug lines

up with the inlet and outlet ports of the valveWhen the plug is turned 90 from the open

position, the solid part of the plug blocks theports and stops fluid flow


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BUTTERFLY VALVEBUTTERFLY VALVE

A butterfly valve is a rotary motion valve thatis used to stop, regulate, and start fluidflow.

Butterfly valves are easily and quicklyoperated because a 90 degree rotation of the handle moves the disk from a fullyclosed to fully opened position..


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Larger butterfly valves are actuated by handwheels connected to the stem throughgears that provide mechanical advantageat the expense of speed


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NEEDLE VALVENEEDLE VALVE

A needle valve Is used to make relativelyfine adjustments in the amount of fluid flow.

The distinguishing characteristic of aneedle valve is the long, tapered, needlelikepoint on the end of the valve stem.

This "needle" acts as a disk.


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The longer part of the needle is smaller thanthe orifice in the valve seat and passesthrough the orifice before the needleseats. This arrangement permits a verygradual increase or decrease in the sizeof the opening.


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DIAPH RAM VALVESDIAPH RAM VALVES

When the diaphragm, which is connectedWhen the diaphragm, which is connectedto the stem of the valve by a compressor,to the stem of the valve by a compressor,is pulled away from the bottom of the valveis pulled away from the bottom of the valvebody or weir, the path of the fluid has abody or weir, the path of the fluid has asmooth, streamlined flow. Slurries at lowsmooth, streamlined flow. Slurries at lowpressure that would normally clog mostpressure that would normally clog most

other valve designs easily pass through aother valve designs easily pass through adiaphragmdiaphragm


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